Low noise pneumatic tire

ABSTRACT

Provided is a low noise pneumatic tire in which the noise absorbing member on the inner peripheral surface of the tire is made less likely to be damaged when the pneumatic tire is removed from the rim. The pneumatic tire includes a noise absorbing member of a porous material which is attached to an inner peripheral surface of the tire. In the pneumatic tire, a lubricant is applied to the inner peripheral surface of the noise absorbing member. Alternatively, both end portions, in a tire width direction, of the inner peripheral surface of the noise absorbing member are covered with protective layers harder than the noise absorbing member.

TECHNICAL FIELD

The present invention relates to a low noise pneumatic tire, andspecifically, to an improvement of a low noise pneumatic tire in which anoise absorbing member of a porous material is disposed on the innerperipheral surface of the tire.

BACKGROUND ART

There are various types of tire noises generated during the running of apneumatic tire. As one of the tire noises, there is cavity resonancesound generated due to the vibration of the air filled in the tire.Heretofore, as a method for effectively reducing the cavity resonancesound, there has been proposed one as shown in FIG. 5, in which a noiseabsorbing member 5 of a porous material such as a polyurethane foam isdisposed on the inner peripheral surface of the tire on the inner sideof a tread portion 1, so that the cavity resonance sound is absorbed bythe noise absorbing member 5 (for example, refer to Patent Documents 1and 2).

When removing such a pneumatic tire T, in which the noise absorbingmember 5 is attached, from a rim R for the purpose of tire rotation orthe like, after the pneumatic tire T is mounted on the rim R, as shownin FIG. 6, a tip end of a lever X of a tire changer is sometimes pressedstrongly against a surface of the noise absorbing member 5. However,since the porous material composing the noise absorbing member isgenerally soft and low in tear strength, there is a problem that thenoise absorbing member is likely to be damaged when the lever of thetire changer is pressed against the surface of the noise absorbingmember as described above. Specifically, a pneumatic tire of which theaspect ratio is smaller and the section height is lower has a tendencythat the noise absorbing member is more likely to be damaged. Oncedamage occurs as described above on the noise absorbing member of thelow noise tire, a stress that is based on deformation of the pneumatictire during the running thereof is concentrated to the damaged spot.Accordingly, the noise absorbing member is gradually removed from theinner peripheral surface of the tire, which leads to a problem thatdesired noise absorbing performance cannot be obtained.

-   Patent Document 1: Japanese patent application Kokai publication No.    Sho62-216803-   Patent Document 2: Japanese patent application Kokai publication No.    2003-63208

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a low noise pneumatictire in which the noise absorbing member on the inner peripheral surfaceis made less likely to be damaged when the pneumatic tire is removedfrom the rim.

A low noise pneumatic tire of the present invention, which achieves theabove-described object, includes a noise absorbing member of a porousmaterial attached to an inner peripheral surface of the tire, in which alubricant is applied to at least both end portions in a tire widthdirection of an inner peripheral surface of the noise absorbing member.

Moreover, another low noise pneumatic tire of the present invention,which achieves the above-described object, includes a noise absorbingmember of a porous material attached to an inner peripheral surface ofthe tire, in which both end portions in a tire width direction on aninner peripheral surface of the noise absorbing member are covered withprotective layers harder than the noise absorbing member.

In accordance with the former low noise pneumatic tire, the lubricant isapplied to at least both of the end portions in the tire width directionon the inner peripheral surface of the noise absorbing member.Accordingly, even if the lever of the tire changer is brought intocontact with the surface of the noise absorbing member when thepneumatic tire mounted on the rim is removed form the rim, the tip endof the lever slips on the surface of the noise absorbing member, thusmaking it possible to prevent the damage of the noise absorbing member.

Moreover, in accordance with the latter low noise pneumatic tire, bothof the end portions in the tire width direction on the inner peripheralsurface of the noise absorbing member are covered with the protectivelayers harder than the noise absorbing member. Accordingly, when thepneumatic tire mounted on the rim is removed form the rim, strongpressing force from the lever of the tire changer is relieved by theabove-described protective layers, thus making it possible to preventthe damage of the noise absorbing member. Hence, even if the pneumatictire after being removed from the rim is reused, there is noconcentration of a stress originated from such a damaged spot, and abreakage is less likely to occur. Accordingly, the noise absorbingperformance of the noise absorbing member can be maintained for a longperiod of time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a meridian cross-sectional view showing a state where a lownoise pneumatic tire according to an embodiment of the present inventionis mounted on a rim.

FIG. 2 is a meridian cross-sectional view showing a state where a lownoise pneumatic tire according to another embodiment of the presentinvention is mounted on the rim.

FIG. 3 is a perspective view showing a noise absorbing member attachedto the pneumatic tire of FIG. 2, in a state of partially being cutaway.

FIG. 4 is a perspective view showing a noise absorbing member accordingto another embodiment, in a state of partially being cutaway.

FIG. 5 is a perspective view showing a conventional low noise pneumatictire, in a state of partially being cutaway.

FIG. 6 is an explanatory view showing a cross-section of the low noisepneumatic tire of FIG. 5 when the low noise pneumatic tire is removedfrom the rim.

BEST MODES FOR CARRYING OUT THE INVENTION

A description will be made below of a low noise pneumatic tire of thepresent invention with reference to the embodiments shown in thedrawings.

FIG. 1 is a meridian cross-sectional view showing a state where a lownoise pneumatic tire is mounted on a rim according to an embodiment ofthe present invention.

Such a pneumatic tire T is composed of a pair of right and left sidewall portions 3, 3 as well as a pair of right and left bead portions 2,2 are formed respectively on the right and left sides of a tread portion1. Though not shown, besides the above, a carcass layer that forms aframe of the tire, a belt layer that gives rigidity to the treadportion, and the like are provided in the tire body. Onto an innerperipheral surface 1 a of the tire as described above, a noise absorbingmember 5 is attached by an elastic fixing band 6. The noise absorbingmember 5 is composed of a belt-like porous material, and is attachedannularly so as to go along the inner peripheral surface 1 a of thetire. Moreover, an inner peripheral surface 5 a of the noise absorbingmember 5 is entirely applied with a lubricant 4. As shown in FIG. 1, theinner peripheral surface 1 a of the pneumatic tire T forms a cavity incombination with the rim R, and no lubricant is present on the innerperipheral surface of the tire.

When the above-described pneumatic tire T in the state of being mountedon the rim R is removed from the rim R by using a tire changer, as shownin FIG. 6, a tip end of a lever X of the tire changer sometimes pressesthe surface of the noise absorbing member 5. However, in theabove-described pneumatic tire T, the lubricant 4 is applied to thesurface of the noise absorbing member 5, and accordingly, even if thelever X is pressed against the surface concerned, the tip end thereofslips on the surface, and thereby does not damage the noise absorbingmember 5. Accordingly, even if the pneumatic tire concerned is reusedafter being removed from the rim, the noise absorbing member is notbroken at an early stage, but can exert good noise absorbing performancefor a long period of time.

An applied region of the noise absorbing member 5 with the lubricant 4only needs to be at least both end portions in the tire width directionof the inner peripheral surface 5 a. Preferably, the entire region ofthe inner peripheral surface 5 a is applied with the lubricant 4.Besides such a case as described above where the lubricant 4 is appliedto the inner peripheral surface 5 a of the noise absorbing member 5, thelubricant 4 may be applied also to an outer peripheral surface side ofthe noise absorbing member 5. The lubricant is applied also to the outerperipheral surface of the noise absorbing member, whereby contactfriction resistance between the noise absorbing member and the innerperipheral surface of the tire can be reduced. Accordingly, durabilityof the noise absorbing member can be enhanced.

Types of the lubricant are not particularly limited; however, forexample, wax, graphite, molybdenum disulfide, boron,polytetrafluoroethylene, talc, silicone, liquid paraffin, mineral oil,and the like can be illustrated. Only one type of these lubricants maybe used singly, or two or more types thereof may be used in combination.As the above-described wax, there can be used natural wax;Fischer-Tropsch wax; hydrocarbon synthesis wax of a polyethylene and thelike; fatty acid ester wax; fatty acid amid; ketones/amines; hardenedcaster oil; and the like. Also with regard to these waxes, only one typethereof may be used singly, or two or more types thereof may be used incombination.

FIG. 2 shows a state where a low noise pneumatic tire is mounted on therim according to another embodiment of the present invention, and FIG. 3shows a noise absorbing member attached to an inner surface of theabove-described tire, together with an elastic fixing band to attach thenoise absorbing member.

A tire body of such a pneumatic tire T of FIG. 2 is the same as that inthe case of the embodiment of FIG. 1, and accordingly, a description ofthe tire body will be omitted. Referring also to FIG. 3 together withFIG. 1, a noise absorbing member 5 is composed of a belt-like porousmaterial as in FIG. 1, and such a belt-like member is attached annularlyso as to go along a inner peripheral surface 1 a of the tire in aninside of the tread portion 1. On the inner peripheral surface 5 a ofthe noise absorbing member 5, protective layers 7 and 7 are provided onboth of the end portions thereof in the tire width direction, and theprotective layers 7 are composed of a hard resin sheet or a metal sheet,which is higher in hardness than the noise absorbing member 5.

The above-described protective layers 7 may be provided on the noiseabsorbing member 5 as in an embodiment shown in FIG. 4. Specifically,both side surfaces of the noise absorbing member 5 may be individuallyformed into inclined surfaces 5 b and 5 b, and both of the inclinedsurfaces 5 b and 5 b and both of the end portions of the innerperipheral surface 5 a in the tire width direction may be coated withthe protective layers 7 and 7.

As described above, at least both of the end portions of the innerperipheral surface 5 a of the noise absorbing member 5 are coated withthe protective layers 7 and 7. In such a way, when the pneumatic tire Tmounted on the rim is removed from the rim R by using the tire changer,the tip end of the lever X is brought into direct contact with thesurface of the protective layer 7, thus making it possible to preventthe noise absorbing member 5 from being damaged. Hence, as in theembodiment of FIG. 1, durability of the noise absorbing member 5 isenhanced and good noise absorbing performance is maintained for a longperiod of time.

In the present invention, a hard material for the protective layers 7 isnot particularly limited, but includes the hard material higher inhardness than the noise absorbing member 5; however, should preferablybe composed of resin sheets or metal sheets. As a material for the resinsheets, there are polypropylene, polyethylene, polyester, polyamide, andthe like. As a material for the metal sheets, there are steel, copper,and the like, and stainless steel is particularly preferable.

Preferably, a thickness of the protective layers is set at 0.05 to 1.0mm. When the thickness of the protective layers is smaller than 0.05 mm,it is difficult to prevent the noise absorbing member from being damagedby the contact thereof with the tip end of the lever. Meanwhile, whenthe thickness of the protective layers is larger than 1.0 mm, bendingrigidity of the noise absorbing member is increased, and accordingly, itis difficult to attach the noise absorbing member along the innerperipheral surface of the tire.

Preferably, a width of the protective layers in the tire width directionis set at 10 to 40 mm. When the width of the protective layers issmaller than 10 mm, it is difficult to prevent the noise absorbingmember from being damaged by the contact thereof with the tip end of thelever. Moreover, when the width of the protective layers is larger than40 mm, a coated area of the protective layers to the inner peripheralsurface of the noise absorbing member is too large, resulting in adecrease of the noise absorbing performance.

Moreover, in the embodiment of FIG. 2, more preferably, the tire cavitysides of the protective layers 7 are applied with the lubricant used inthe embodiment of FIG. 1. The lubricant is used as described above, inorder for the lever of the tire changer to slip on the protective layers7. Accordingly, such an effect of preventing the damage of the noiseabsorbing member by the protective layers can be further enhanced.

Note that, in the embodiments of FIG. 1 and FIG. 2, the noise absorbingmember 5 is attached to the inner peripheral surface 1 a of the tire bydisposing the elastic fixing band 6 on the outer periphery side of thenoise absorbing member 5; however, the elastic fixing band 6 may bedisposed and attached to the inner peripheral surface 5 a side of thenoise absorbing member 5.

The above-described low noise pneumatic tire of the present inventioncan be applied to a general pneumatic tire. However, the low noisepneumatic tire concerned can exert a large effect particularly in thecase of being applied to a pneumatic tire with the aspect ratio of 45%or less, which is likely to cause the damage of the noise absorbingmember.

Example

As a common condition, the following was set, where a noise absorbingmember, made of a urethane foam, with a thickness of 20 mm and a widthof 180 mm was attached to an inner peripheral surface of a low noisepneumatic tire with a size of 225/40R18 by an elastic fixing band, madeof polypropylene resin, with a width of 20 mm and a thickness of 2 mm.Then, the following low noise pneumatic tires were individually built,which are: a low noise pneumatic tire in which polyethylene wax wasapplied to an inner peripheral surface of the noise absorbing member(Example 1); a low noise pneumatic tire in which polypropylene resinsheets (protective layers) with a width of 20 mm and a thickness of 0.5mm were covered on both end portions in the tire width direction of theinner peripheral surface of the noise absorbing member (Example 2); alow noise pneumatic tire in which the polyethylene wax was applied tosurfaces of the protective layers in the tire configuration of Example 2(Example 3); and a low noise pneumatic tire in which the surface of thenoise absorbing member was not subjected to any process (Conventionalexample).

For each of these four types of pneumatic tires, fifty times repeatedwas work of removing these pneumatic tires from a rim by using the sametire changer after mounting the pneumatic tires concerned to the rim.Then, the number of times that damage occurred on the surface of eachnoise absorbing member was investigated. Results of the investigationsare shown in Table 1.

TABLE 1 Conventional Example 1 Example 2 Example 3 example Occurrence ofthe 4 1 0 17 number of times that noise absorbing member is damaged

As is clear from the results shown in Table 1, in Examples 1 and 2, theoccurrences of the damage on the noise absorbing member are drasticallyreduced compared to the conventional example.

What is claimed is:
 1. A low noise pneumatic tire, mounted on a rim,comprising: an inner peripheral surface of the tire forming a cavity incombination with the rim, and comprising: a noise absorbing member of aporous material which is attached to the inner peripheral surface of thetire, wherein one end portion in the tire width direction on the innerperipheral surface of the noise absorbing member is covered with a firstprotective layer harder than the noise absorbing member, and wherein theother end portion in the tire width direction on the inner peripheralsurface of the noise absorbing member is covered with a secondprotective layer harder than the noise absorbing member and completelyseparate from the first protective layer.
 2. The low noise pneumatictire according to claim 1, wherein both side surfaces in the tire widthdirection of the noise absorbing member are formed into inclinedsurfaces, and the inclined surfaces are covered with the protectivelayers together with both of the end portions in the tire widthdirection.
 3. The low noise pneumatic tire according to claim 2, whereina lubricant is applied to surfaces of the protective layers.
 4. The lownoise pneumatic tire according to claim 2, wherein the width of each ofthe protective layers is between 10 to 40 mm.
 5. The low noise pneumatictire according to claim 2, wherein the thickness of each of theprotective layers is between 0.05 to 1.0 mm.
 6. The low noise pneumatictire according to claim 2, wherein the aspect ratio of the pneumatictire is 45% or less.
 7. The low noise pneumatic tire according to claim1, wherein each of the protective layers is formed of a resin sheet. 8.The low noise pneumatic tire according to claim 7, wherein a lubricantis applied to surfaces of the protective layers.
 9. The low noisepneumatic tire according to claim 7, wherein the width of each of theprotective layers is between 10 to 40 mm.
 10. The low noise pneumatictire according to any claim 7, wherein the thickness of each of theprotective layers is between 0.05 to 1.0 mm.
 11. The low noise pneumatictire according claim 1, wherein a lubricant is applied to surfaces ofthe protective layers.
 12. The low noise pneumatic tire according toclaim 1, wherein the width of each of the protective layers is between10 to 40 mm.
 13. The low noise pneumatic tire according to claim 1,wherein the thickness of each of the protective layers is between 0.05to 1.0 mm.
 14. The low noise pneumatic tire according to claim 1,wherein the aspect ratio of the pneumatic tire is 45% or less.